"I happen to hate the phrase ecosystem services, and my colleagues in business and government don't like it either…but it's what we're stuck with." That's Peter Kareiva, chief scientist at The Nature Conservancy, "What we mean by ecosystem services are the products or functions that nature provides which are of great value for people."

"In this world, cost benefit analysis and dollars are how decisions get made…When nature and the benefits that nature are not converted to dollars then it can't be on the table for those discussions and, in a way, nature's not getting credit for what it's doing."

That lack of credit often means a lack of concern for the natural world as development decisions get made. But ignoring nature imposes a steep cost of its own. Consider the mysterious ailment killing bees and thus risking the ecosystem "service" of pollination. Or the devastation Hurricane Katrina visited on New Orleans partially because of the disappearance of the storm protection offered by wetlands.

Of course, any dollar values on natural services will be wrong because it's extremely hard to accurately account for the value of, say, clean air. But Kareiva and others argue that putting zero value on nature is a much bigger mistake.